Journal of Neuroscience, Vol 3, 739-747, Copyright © 1983 by Society for Neuroscience
Cyclic adenosine 3':5'-monophosphate phosphodiesterase and its role in learning in Drosophila
SL Shotwell
Drosophila carrying the X-linked mutation dunce (dnc) showed poor learning
in a negative reinforcement olfactory conditioning paradigm (Dudai, Y.,
Y.-N. Jan, D. Byers, W.G. Quinn, and S. Benzer (1976) Proc. Natl. Acad.
Sci. U.S.A. 73: 1684-1688). More recently, dnc flies were shown to have
reduced activity for one of two cAMP phosphodiesterases (PDEs) present in
normal flies, PDE II, whereas PDE form I was unaffected (Byers, D., R. L.
Davis, and J. A. Kiger, Jr. (1981) Nature 289: 79-81). A micro-assay
technique is described that allows the separate measurement of PDE I and
PDE II in crude extracts, based on specific inhibition of PDE I [3H]cAMP
hydrolysis by cGMP. Using this technique, PDE II is shown to occur normally
at high specific activity in the nervous system, consistent with the
hypothesis that this enzyme plays a role in neuronal function. Reduced PDE
II activity correlates with poor learning in dnc flies at three
developmental stages (first and third instar larva and adult), as well as
in response to genetic modification of dnc gene activity. Biochemical and
genetic experiments fail to reveal any abnormal regulation of PDE II in
dnc. The specific activity of PDE II is shown to correlate in a one to one
fashion with the level of normal dnc gene (dnc+) activity at five different
doses of dnc+. These results support the hypothesis that PDE II represents
the primary product of the dnc gene, indicating a role for this enzyme in
Drosophila learning.